Web services also called as web application services, usually as combination of programming and data and it’s defined by W3C as a software system designed to support interoperable machine to machine interaction over a network. It’s common usage the term refers to clients and servers that communicate over the HTTP or HTTPS protocol used on the web. A web services provide access to software systems over the internet using standard protocols.

In the web services consist of a remote procedure call ( RPC ) interface to a search source that enables our client application to invoke operations on the search source over a network. We have web service application with parameters specified by the interface in a message and send a message to the specified URL requesting service. The request and response messages are implemented as input and output arguments to a function call that uses the URL to invoke the operation.

We can build the web service application with some of the framework web service is available, such as NuSOAP with SOAP, in the PHP and others. Web services builds on five key protocols : HTTP/HTTPS, XML, UDDI, WSDL and SOAP. Web service use standard protocol HTTP / HTTPS and standard data format for implementing both underlying service interfaces and data exchange format is XML.

WSDL definition and implementation

WSDL definition and implementation

SOAP is a simple text based protocol for exchanging information between two endpoints and based on a stateless with one way message exchange protocol. SOAP use a simple request and response model where the requestor acting as the SOAP client and provider of request services acting as a SOAP server and the provider provides the requested services across a SOAP interface. SOAP use XML format as messaging format and support two styles : self describing as document style message and encoded with SOAP remote procedure calls ( RPCs ).

XML as the standard language for web services and based on the Standard Generalized Markup Language ( SGML ). It’s a general purpose specification for creating custom markup language for information systems in sharing structured data via internet. XML documents normally begin with a prolog section as the root element. The first statement in the prolog is XML declaration that begin with literal string “Word Wide Web Consortium ( W3C ) website.

The Web Services Description Language ( WSDL ) defines services as collection of network endpoints that are called ports and based on XML language to provide a web services. WSDL also is often used in combination with SOAP and an XML schema to provide web services over the internet. WSDL abstracts the endpoint definitions from their implementation by separating the messages that can be exchanged and the operations that can be performed from the specific protocols and specifications being used.

Universal Description, Discovery and Integration ( UDDI ) is a platform independent with a standard way of registering and discovering web services and it’s built on the concept of a distributed and XML registry where service providers can register their services along with descriptions of and pointer to those services. The UDDI was integrated into the Web Services Interoperability (WS-I) standard as a central pillar of web services infrastructure. We can find more information about UDDI at UDDI website.

In this discussion, we have been discussing about definition and elements of web services. See more information how to implementation of web service at the next discussion.

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